The present invention pertains to a device useful in an optical connector containing multi-fiber ferrule containing optic fibers. In particular, the inventive device is an alignment element that fits into a housing such that when a connector is slidably attached to the housing, the alignment element forces the connector against a reference surface thereby ensuring proper alignment of the connectors.
The use of optical fibers for high-volume, high-speed communication is well established. As the volume of transmitted information grows, the use of optical fiber cables that have multiple optical fibers and of systems using multiple optical fiber cables has increased.
Fiber optic terminations are evolving from single terminations to mass terminations. Within the past few years, ribbonized multi-fiber cables have been developed. In conjunction with these cable development efforts, multi-fiber mounting ferrules also have been developed.
The design of traditional electronic cabinets is now being altered to accommodate optical and opto-electronic devices. In traditional cabinet designs, the cabinet contains a box having a backplane and plurality of internal slots or racks, generally parallel to each other. Components are mounted on planar substrates, commonly referred to as xe2x80x9ccircuit boardsxe2x80x9d or xe2x80x9cdaughter cards,xe2x80x9d which are designed to slide into the slots or racks within the cabinet.
An example of a backplane application is the interconnection of telephone switching equipment where the cards, having optical and electronic telecommunication components, typically disposed on daughter cards, are slid into cabinets. As with electrical cables, the need exists to provide for a means to allow the fiber signals to pass through the backplane of the cabinets. Another need is to have a removable fiber termination from the front side and the backside of the backplane. Furthermore, when the cards are inserted and removed from a rack coupled to the backplane, coupling and uncoupling of the optical connections in the card occurs in a blind mating manner causing added alignment challenges.
In order to maintain appropriate transmission of light signals, optical fiber ends are to be carefully aligned along three movement (x, y, and z in Cartesian coordinate system) axes, as well as angularly. As the number of optical fibers to be aligned increases, alignment challenges also increase. Blind mating of a card-mounted component to a backplane connector has been found to create special alignment challenges along the axis of interconnection.
For the purposes of the present description, the axis of interconnection is called the longitudinal or x-axis and is defined by the longitudinal alignment of the optical fibers at the point of connection. Generally, in backplane applications, the longitudinal axis is collinear with the axis of movement of the cards and the axis of connection of the optical fibers in and out of the cabinets. The lateral or y-axis is defined by the perpendicular to the x-axis and the planar surface of the card. Finally, the transverse or z-axis is defined by the orthogonal to the x-axis and the backplane surface. The angular alignment is defined as the angular orientation of the card with respect to the x-axis.
Some skilled in the art have tried to address the ferrule alignment issue. For example, U.S. Pat. No. 5,619,604 (Shiflett et al.) discloses a multi-fiber optical connector using a multi-fiber ferrule such as a mechanical transfer (MT) connector that can be mated with and received by an optical receptacle. Multiple alignment features help align and mate the connector to another multi-fiber object. The connector has a guide prong beneath which is mounted the ferrule. The prong provides a reference surface that functions as a pre-alignment mechanism for the ferrule. The connector also has a U-shaped enclosure containing a spring tab. In use, the reference surface engages the upper surface of the ferrule while the spring tab engages the lower surface of the ferrule and forces it against the reference surface.
The need remains for other connector systems that provide a repeatable and cost effective way to mate ferrules.
One of the challenges in a mechanical system, such as the present multi-fiber connector system, stems from the fact that most of the components are precision molded and machined. As such, the dimensions of the components consistently need to be as near to the design specification as possible for repeated alignment of the components. Holding the components to precise target dimensions (i.e., dimensions that can deviate from one another only in the 0.001 inch range (0.254 mm)) can be difficult and very expensive for molded and machined parts. Even if the components are consistently held to the target dimensions when fabricated, in use the components may be exposed to environmental conditions that may slightly change their dimensions. Most of the components can be used in applications lasting up to twenty years, further increasing the possibility of dimensional changes. The present invention provides for a cost effective approach to align the components that may have slight dimensional deviations, caused in the manufacturing process, caused by environmental changes, caused by extended use, or caused by a combination of these and other factors.
The present invention relates to an optical fiber interconnect system that provides alignment of the ferrules in the x, y, and z directions by use of a unique alignment element. In some embodiments, the inventive interconnect system provides for interconnecting arrays of optical fiber cables in an individual or in a collective fashion. As used herein, the term xe2x80x9cbackplanexe2x80x9d refers to an interconnection plane where a multiplicity of interconnections may be made, such as with a common bus or other external devices. In very brief summary, the present invention provides for an alignment element exhibiting spring-like behavior where the alignment element provides a deflection force against ferrule housings to align the ferrules residing therein. The inventive connector system comprises (a) a housing comprising at least one passageway, each passageway having a first end, a second end opposite the first end, and a reference surface; (b) at least one first optical connector slidably engaged into the first end of the passageway, each first optical connector comprising a ferrule housing and a first ferrule disposed inside the ferrule housing, the first ferrule having at least one port, the ferrule housing having first surface opposite a second surface; and (c) an alignment element. As the alignment element engages the first surface of the ferrule housing, the alignment element forces the second surface of the ferrule housing against the reference surface.
In one preferred embodiment, the present invention provides for a multi-fiber optic connector system comprising: (a) a first housing assembly comprising a first portion having at least one first cavity, a second portion having at least one second cavity, each second cavity having a reference surface and a first groove and wherein the first and second portions are aligned such that the first cavity and the second cavity form a passageway, at least one alignment element disposed on the first groove of the second portion; and (b) at least one first optical connector comprising a first ferrule having a plurality of ports, the first ferrule disposed inside a ferrule housing. When the first optical connector is inserted into the first portion and resides in the passageway, the alignment element contacts the first ferrule housing and forces it against the reference surface.
In the present invention, ferrule alignment can be achieved in various ways. For example, the first and second cavities, the ferrule housing, and the protrusions, by virtue of their size and shape, form the coarse alignment. Because, as discussed above, the dimensions of these components can vary, the fine alignment is achieved by use of the alignment element.
Unlike U.S. Pat. No. 5,619,604, the present invention does not use a tab to push the ferrule directly against a reference surface. Instead, the present invention uses a unique alignment element to guide a ferrule housing and/or a protrusion against a reference surface. One of the advantages of the present invention is that, by virtue of the design, the ferrules are protected inside a housing and are allowed to float inside the housing. The term xe2x80x9cfloatxe2x80x9d as used in the previous sentence means generally that the ferrules have some freedom of movement in the y and z directions so that as the ferrules are being mated during interconnection or as the ferrules are exposed to various environmental conditions, the probability of having the ferrules mate or stay mated, espectively, is increased.